ZFS: unlimited arc cache growth?

Alexander Leidinger Alexander at Leidinger.net
Fri Apr 17 06:06:11 PDT 2009


to fs@, please CC me, as I'm not subscribed.

I monitored (by hand) a while the sysctls kstat.zfs.misc.arcstats.size  
and kstat.zfs.misc.arcstats.hdr_size. Both grow way higher (at some  
point I've seen more than 500M) than what I have configured in  
vfs.zfs.arc_max (40M).

After a while FS operations (e.g. pkgdb -F with about 900 packages...  
my specific workload is the fixup of gnome packages after the removal  
of the obsolete libusb port) get very slow (in my specific example I  
let the pkgdb run several times over night and it still is not  

The big problem with this is, that at some point in time the machine  
reboots (panic, page fault, page not present, during a fork1). I have  
the impression (beware, I have a watchdog configured, as I don't know  
if a triggered WD would cause the same panic, the following is just a  
guess) that I run out of memory of some kind (I have 1G RAM, i386, max  
kmem size 700M). I restarted  pkgdb several times after a reboot, and  
it continues to process the libusb removal, but hey, this is anoying.

Does someone see something similar to what I describe (mainly the  
growth of the arc cache way beyond what is configured)? Anyone with  
some ideas what to try?


When you go out to buy, don't show your silver.

http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137

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